The present investigation focused on screening of a new potent strain for laccase production and optimizing the process parameters to achieve the maximum enzymatic decolourization of textile azo dye Congo red. Seven hydrocarbonoclastic bacterial strains were selected as positive in laccase production in solid medium using 2,6 dimethoxyphenol as an enzyme activity indicator. The best enzyme producer Pseudomonas extremorientalis BU118 showed a maximum laccase activity of about 7000 U/L of wheat bran under solid-state conditions. The influence of different concentrations of dye, enzyme, salt and various incubation times on Congo red decolourization was studied using response surface methodology to find the optimum conditions required for maximum decolourization by P. extremorientalis laccase. The enzyme exhibited a remarkable colour removal capability over a wide range of dye and salt concentrations. The above results show the potential use of this bacterial laccase in the biological treatment of the textile effluent.

A number of Pseudomonas strains function as inoculants for biocontrol, biofertilization, and phytostimulation, avoiding the use of pesticides and chemical fertilizers. Here, we present a new metabolically versatile plant growth-promoting rhizobacterium, Pseudomonas rhizophila S211, isolated from a pesticide contaminated artichoke field that shows biofertilization, biocontrol and bioremediation potentialities. The S211 genome was sequenced, annotated and key genomic elements related to plant growth promotion and biosurfactant (BS) synthesis were elucidated. S211 genome comprises 5,948,515 bp with 60.4% G+C content, 5306 coding genes and 215 RNA genes. The genome sequence analysis confirmed the presence of genes involved in plant-growth promoting and remediation activities such as the synthesis of ACC deaminase, putative dioxygenases, auxin, pyroverdin, exopolysaccharide levan and rhamnolipid BS. BS production by P. rhizophila S211 grown on olive mill wastewater based media was effectively optimized using a central-composite experimental design and response surface methodology (RSM). The optimum conditions for maximum BS production yield (720.80 ± 55.90 mg/L) were: 0.5% (v/v) inoculum size, 15% (v/v) olive oil mill wastewater (OMWW) and 40°C incubation temperature at pH 6.0 for 8 days incubation period. Biochemical and structural characterization of S211 BS by chromatography and spectroscopy studies suggested the glycolipid nature of the BS. P. rhizophila rhamnolipid was stable over a wide range of temperature (40–90°C), pH (6–10), and salt concentration (up to 300 mM NaCl). Due to its low-cost production, emulsification activities and high performance in solubilization enhancement of chemical pesticides, the indigenous BS-producing PGPR S211 could be used as a promising agent for environmental bioremediation of pesticide-contaminated agricultural soils.

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A new bioflocculant named pKr produced by hydrocarbonoclastic strain Kocuria rosea BU22S (KC152976) was investigated. Gas chromatography-flame ionization detector (GC-FID) analysis confirmed the high potential of the strain BU22S in the degradation of n-alkanes. Plackett-Burman experimental design and response surface methodology were carried out to optimize pKr production. Glucose, peptone and incubation time were found to be the most significant factors affecting bioflocculant production. Maximum pKr production was about 4.72 ± 0.02 g/L achieved with 15.61 g/L glucose, 6.45 g/L peptone and 3 days incubation time. Chemical analysis of pKr indicated that it contained 71.62% polysaccharides, 16.36% uronic acid and 2.83% proteins. Thin layer chromatography analysis showed that polysaccharides fraction consisted of galactose and xylose. Fourier transform infrared analysis revealed the presence of many functional groups, hydroxyl, carboxyl, methoxyl, acetyl and amide that likely contribute to flocculation. K. rosea pKr showed high flocculant potential using kaolin clay at different pH (2-11), temperature (0-100°C) and cation concentrations. The bioflocculant was particularly effective in flocculating soluble anionic dyes, Reactive Blue 4 and Acid Yellow, with a decolorization efficiency of 76.4% and 72.6%, respectively. The outstanding flocculating performances suggest that pKr could be useful for bioremediation applications.